SUN-SPOTS AND FAMINES. 



131 



ilshed his long-continued researches, indicating 

 the existence of a cycle in magnetic variations, 

 occupying on an average ten and a third years. 

 Sir Edward Sabine, in 1S52, carried forward the 

 work by a paper in the "Transactions of the 

 Royal Society." He subsequently communicated 

 the results of a series of records between 1859 

 nnd 1864, of the horizontal and vertical force 

 magnetometers at the Kew Observatory, with a 

 note showing their connection with the sun- 

 spots and giving interesting historical details. 

 He observed, too, that the fluctuations of the 

 magnet were almost invariably accompanied by 

 displays of the aurora borealis, and came to the 

 conclusion that auroral displays occur most fre- 

 quently in years of maximum sun-spots. Dr. 

 Wolf, now of Zurich, and M. Gautier, of Geneva, 

 had independently remarked, in 1852, the coin- 

 cidence of Lamont's decennial magnetic period 

 with Schwabe's period of sun-spots. In 1865 

 Prof. Loomis, of Yale College, supplied further 

 evidence on the range of magnetic declination 

 and auroras, in their relation to sun-spots. He 

 concluded that the auroras observed in Europe 

 and America exhibit a true periodicity, closely 

 following the magnetic periods, but not perfectly 

 identical with them. He believed that a sun- 

 spot is the result of a disturbance of the sun's 

 surface, with some emanation from the sun which 

 is felt almost instantly upon the earth. Signor 

 Schiaparelli, in 1875, brought out with great 

 clearness the relations between the sun-spot pe- 

 riods and the variations in the declination of the 

 magnetic needle. In the same year, also, Sophus 

 Tromholdt contributed to the Zeitschrift der os- 

 ierreichixchen, Gesellschaftfiar Meteorohgie a note 

 on the connection of auroras with the sun-spot peri- 

 ods. In 1876 Dr. J. A. Broun presented the re- 

 sults derived from observations of magnetic dec- 

 lination made during nearly a quarter of a cen- 

 tury at Trevandrum. He gave the mean duration 

 of the magnetic cycle at 10.45 years, and sup- 

 plied a very valuable chart showing the decen- 

 nial period of the diurnal range of magnetic dec- 

 lination and sun-spot area from 1784 to 1876. 

 The curves of this elaborate and most interesting 

 chart place the general coincidence of the mag- 

 netic and sun-spot cycles in a clear light. Dr. 

 Broun came to the conclusion that while the 

 II sun-spot activity is not an exact measure of mag- 

 netic action, " each is a distinct result due to the 

 same cause.' 1 The whole question has, during 

 the present summer (May, 1877), been reviewed 

 by Prof. Balfour Stewart, a distinguished work- 

 er in the same field. He has exhibited the solar 



spots, magnetic declination, and aurora displays, 

 from 1776 to 1872, in curves which follow each 

 other with an indisputable coincidence. He fur- 

 ther examines the connection of these three co- 

 incident cycles with planetary configurations : a 

 question discussed by Mr. Fritz in the " Proceed- 

 ings of the Royal Society" in 1871, and previ- 

 ously studied with much care by Dr. De la Rue 

 and Prof. Balfour Stewart, at Kew (1854-'66). To 

 sum up : magnetic observers now hold that not 

 only do the spasmodical affections of the needle 

 follow curves closely coincident with the solar 

 spots, "but its diurnal oscillations are not less 

 dependent on the state of the sun's surface." 



Such magnetic disturbances have very prac- 

 tical results. Telegraphy and telegraphic lines 

 form one of the most conspicuous of the new 

 commercial undertakings of our day. During 

 periods of maximum magnetic disturbance, tele- 

 graphic communication between points so close 

 as London and Dover is sometimes interrupted. 

 Mr. Charles V. Walker, superintendent of tele- 

 graphs, presented an important paper in 1861 to 

 the Royal Society, on magnetic storms and earth- 

 currents. He described the remarkable disturb- 

 ances in communication which took place in 1848, 

 a year of maximum sun-spots, and in the autumn 

 of 1859, just before the next year of maximum 

 sun-spots (1860). The first period of disturbance 

 appeared to his staff to be an altogether " ab- 

 normal " one. " We did not then know," writes Mr. 

 Walker, "as we now do, that these disturbances 

 have a cycle of about eleven years from the 

 maximum period of activity to the next maxi- 

 mum." An idea of -the violence of such mag- 

 netic storms may be derived from the Dover 

 clerk's entry on September 2, 1859 : " This 

 morning, on opening the office, I found the nee- 

 dles of both instruments firmly blocked over to 

 the left, and, although the handles were firmly 

 held over to the right to counteract the power, 

 to my surprise I found that our battery-power 

 had not the slightest effect. ... I am sorry to 

 say that there is not the slightest possibility of 

 our working the instrument ; needles continuing 

 firmly fixed over, and this has continued for up- 

 ward of half an hour." This disturbance was 

 of such magnitude and of so long duration that 

 the operators were unable to supply an adequate 

 narrative of it, as " they were at their wits' end 

 to clear off the telegrams which accumulated 

 in their hands, by other less affected but less 

 direct routes." Mr. Walker has retained no 

 record of the earth-currents during the last pe- 

 riod of maximum sun-spots (1S70), but the dis- 



